In the past various types of electrical switches, such as multiple push button switches for instance, have been employed in conjunction with a wide variety of electrical equipment. For example, multiple push button switches have been frequently employed in household appliances, such as for instance blenders, food processors, electric ranges, washing machines, and air conditioners or the like, and such push button switches were operable to effect the selection of one of a variety of possible operating modes of such appliances. Frequently, such a multiple push button switch will have one push button corresponding to each possible mode of the appliance, including its "off" mode, and will be mechanically arranged so that only one push button may be actuated or depressed at any given time to select the desired operating mode of the appliance.
One prior art multiple push button switch of the type discussed above is illustrated in the Andrews U.S. Pat. No. 2,431,904. This patented push button switch discloses a plurality of adjacent laterally movable sliders within a switch housing with such sliders having numerous inclined or working surfaces adapted to be engaged by several push buttons of the switch. Depression of a respective one of these buttons is effective to move one or several of the sliders to a position determined by the particular working surface engaged by the depressed push button. The sliders also include cam surfaces which selectively engage contact supporting springs or switch blades with a particular combination of such cam surfaces determining the blade positions. Thus, a cam surface may engage a switch blade to prevent electrical connection between a contact supported on that blade and a fixed contact within the switch housing when the particular slider is in one position while allowing or forcing the fixed and blade supported contacts together when the slider is moved to a different position.
A prior art variation of the above discussed type of push button switch is disclosed in the Vermeulen U.S. Pat. No. 2,878,329 which is incorporated herein by reference. In this patent, push buttons selectively engage inclined or working surfaces on a plurality of sliders, and those sliders, in turn, include cam surfaces for actuating switch blades. The possibility of flashover occurring during switching from one electrical interconnection to another is minimized by positioning certain of the working surfaces more remote from the slider engaging portion of the push buttons than others of the working surfaces so that a delay in switch contact operation is achieved. In other words, in Vermeulen, upon depression of a push button, certain sliders begin their movement prior to the commencement of movement of others of the sliders.
In the prior art switches of the type disclosed by the above discussed Andrews and Vermeulen patents, transition from any one switch operating mode directly to any other switch operating mode is simply achieved by depressing the push button corresponding to that next operating mode. The prior art is also believed to suggest switching devices with built-in conditions or interlocks so that specified switch action sequences between switch operating modes do not occur. It is believed that a very elementary example of this type switch might be a three-position rotary switch wherein it is not possible to go from one extreme switch position to the other extreme switch position without first passing through the middle switch position. Further, it is also believed that limitations on the sequence of multiple push button switch actuation may also be known. For example, an early appliance control switch illustrated in the Kimball U.S. Pat. No. 2,228,167 required depression of an "off" or release button of such switch to effect the switching thereof from any one appliance energizing switch position to another appliance energizing switch position. A further example outside the appliance control art is found in the Schuh U.S. Pat. No. 3,675,504 which disclosed a taximeter having a "vacant" key which had to be operated thereby to unlock the other keys for subsequent operation.